The invention relates to a method and a device for cleaning a section of an optical waveguide removed from its jacket, in particular in preparation for a splicing procedure, in which two ends of cleaned optical waveguide sections are welded thermally together.
In order to be able to connect together light-directing fibers, frequently also referred to as optical waveguides or optical fibers, the ends of the optical waveguides have to be welded thermally together. This procedure is also referred to as splicing. Splicing generally takes place in special splicing devices, with the two optical waveguides to be connected together being positioned in relation to each other before the actual splicing procedure such that their end surfaces face each other without any lateral displacement. The actual splicing procedure then takes place by drawing an electric arc between two electrodes arranged on opposing sides adjacent to the two end surfaces.
To obtain a good splice connection between two optical waveguides, i.e. a connection with little optical attenuation and a high level of mechanical tensile strength, the end sections of the optical waveguide have to be thoroughly prepared before the actual splicing procedure. This includes both very precise separation, to produce as flat an optical waveguide end surface as possible by means of a perpendicular, sharp-edged cut, and the cleaning of the optical waveguide end section removed from its jacket. Cleaning is necessary, as when removing the jacket, during which process the coating is generally removed from the optical waveguide by means of a suitable tool, residues of the jacket frequently remain on the removed optical fibers. These residues can impede subsequent welding of the optical waveguides. Therefore a high quality spliced connection requires a cleaning procedure during which all the coating residues are removed.
For optimum preparation for splicing, in addition to the above-mentioned precise separation and complete cleaning, it is also necessary to straighten the optical waveguide end sections. Straightening is necessary for precise positioning of the optical waveguide end sections during the splicing procedure. As the optical waveguide jacket is generally made of plastic and therefore frequently produces internal stresses, which result in distortion of the optical waveguide, it is necessary to reduce these internal stresses by heating the optical waveguide. The section of an optical waveguide, which is not removed from its jacket, can then be straightened. Such alignment for example is achieved by heating the optical waveguide sections still with their jacket in a furnace, which for example has two heated plates at a distance from each other.
According to the prior art the optical waveguide end sections are generally cleaned manually by wiping the optical waveguide end section with the least fluffy cloth possible. The cloth is soaked with a cleaning agent, preferably alcohol. Alcohol has the advantage that it has a very good cleaning action and on evaporation leaves no residues on the cleaned optical waveguide. Manual cleaning with a cloth however has the disadvantage that the cleaning action depends on the skill of the person doing the cleaning. A further disadvantage is that the person doing the cleaning is exposed to toxic vapors when using many cleaning agents.
Another known method for cleaning optical waveguide end sections is cleaning in an ultrasound bath. However this has the disadvantage that alcohol cannot be used because of its combustibility and volatility and it therefore has to be replaced with another less suitable and more expensive cleaning agent.
A device is known from WO 02/44778 A1 for the automatic preparation of optical waveguides for a subsequent splicing procedure. The device has a unit for stripping an optical waveguide, a unit for cleaning the optical waveguide and a separating unit for breaking the optical waveguide, in order to produce an optical waveguide end that is removed from its jacket, cleaned and provided with a flat end surface in a simple fashion.